Source : Webster's Revised Unabridged Dictionary (1913)

Whereupon \Where`up*on"\, adv.
   Upon which; in consequence of which; after which.

         The townsmen mutinied and sent to Essex; whereupon he
         came thither.                            --Clarendon.

Source : WordNet®

whereupon
     adv 1: closely following and in consequence of which; "the Japanese
            refused to import U.S. made cellular phones whereupon
            the U.S. imposed strict tariffs on Japanese exports"
     2: upon which; "the rock whereupon she stood"
     3: in consequence of which; "this is a statement whereat the
        listeners may get angry" [syn: {whereat}]